This invention relates to engine cylinder deactivation apparatus and more particularly to apparatus including a simplified hydraulic circuit providing both cylinder deactivation and air purge functions.
It is known in the art of engine cylinder deactivation to provide switchable hydraulic lash adjusters operable to either actuate the valves of a deactivation cylinder or to maintain the valves closed through lost motion features of the hydraulic lash adjusters. Similar mechanisms may be provided in hydraulic valve lifters which include internally hydraulic lash adjusting mechanisms and so may also be referred to broadly as hydraulic lash adjusters.
Conventional lash adjusters are supplied with pressurized oil through a lash adjuster gallery or lifter gallery to annular feed grooves or intake ports which admit pressurized oil to take up the lash in the valve train between the valve and its associated tappet or other actuator. Lash adjusters and valve lifters with cylinder deactivation mechanisms have additional ports for lock pins, which connect through control passages and a control channel with a valved oil pressure supply. A three-way solenoid-actuated hydraulic control valve may be used to admit oil pressure to the lock pins for cylinder deactivation, or switching, of the lash adjusters in a supply mode of the three-way valve and to exhaust oil pressure from the oil passages and control gallery in an exhaust mode.
Such cylinder deactivation apparatus typically use complex systems of bypass channels and hydraulic bleeds in order to purge air or other gas/vapor from the system to insure consistent response to control signals. This is necessary to provide reliable actuation or deactivation of the switchable hydraulic lash adjusters in the apparatus when the hydraulic control valve is actuated to make a change in operation. These bleed and bypass systems may add considerable complexity to the deactivation apparatus itself. Thus, a simplified system for purging gas/vapor, primarily air, from the hydraulic cylinder deactivation apparatus is desired.
The present invention provides cylinder deactivation apparatus having a simplified hydraulic circuit featuring a single oil supply which supplies oil to both conventional and deactivation valve lifters for lubrication of the mechanism and operation of internal lash adjusters. The single oil supply further provides oil to cylinder deactivation control passages through one or more restricted passages or orifices adjacent the lash adjusters. A control valve in the control passages remains open to drain oil flow from the control passages or closes to prevent the exhaust of oil from the control passages.
When the valve is open, full pressure oil is delivered to the lash adjusting mechanisms while the restricted passages limit oil flow to the control passages. This limits oil pressure in the control passages to a level below that required to operate the deactivation or switching mechanisms of the lash adjusters so that the valves are operated normally and the cylinders are not deactivated. When the valve is closed, pressure in the control passages quickly increases to the oil supply pressure, causing the deactivation mechanisms of the deactivation lifters or lash adjusters to release the lock pins and deactivate the valves of the cylinders having deactivation lifters or lash adjusters. The flow of oil through the control passages when the valve is open is adequate to purge gaseous vapors such as air from the control passages and maintain the system in condition for prompt deactivation of the cylinders when the valve is closed.